Lead base alloy



Patented Feb. 18, 1 941 UNITED STATES LEAD BASE ALLOY Albert J. Phillips, Plainfield, and Albert A. Smith,

Jr., and Paul A. Beck, Metuchen, N. J., assignors to American Smelting and Refining Company, New York, N. Y., a corporation of New Jersey No Drawing. Application June 22, 1989, Serial N0. 280,576

4 Claims.

The present invention provides improved lead base alloys having markedly improved hardness and tensile strength at elevated temperatures, together with substantially improved fatigue strength, which properties render the present alloys very suitable as a bearing alloy.

One of the objectionable factors involved in the production of bearing metals of the usually accepted composition lies in the cost of the components entering the compositions, such compositions being typically, Sb 15%, Sn 5%, Cu 0.5%, As 0.2%, balance lead for a lead base Babbitt metal; and 5.5% Cu, 6.25% Sb, balance tin for a tin-base Babbitt metal.

The above compositions are, respectively, referred to hereinafter as lead-base and tin-base Babbitt metal. In both of these compositions, the tin contents are rather high, being of course very high in the tin-base babbitt, the cost of which results in the use of lead-base babbitt because of the relative cheapness of the latter, notwithstanding its comparatively poorer properties.

One object of the present invention is to provide an improved bearing alloy which is cheaply produced, being even less expensive than leadbase babbitt, and which, possesses properties which are definitely superior to the properties of the typical lead-base and tin-base Babbitt metals.

Other objects of the invention will become apparent as the description proceeds, and the features of novelty will be pointed out with particularity in the appended claims.

More particularly, the present invention relates to an alloy of lead, small but effective amounts of tin, but substantially below 3% thereof, and important amounts of both antimony; and arsenic, the composite amount of which is not less than 13%. Thus, there may be 10-14% Sb, 0.5-0.8% Sn, 2-5% As, balance substantially lead.

The preferred composition, however, is: Sb 12.5%, As 3%, Sn 0.75%, balance substantially lead.

The following table indicates the comparative properties of the present alloy with similar prop- In making the above determination, the hardness tests were made with a 10 m. m. ball, 100

kg. load, for 30 seconds. At 150 C. the test specimens were preheated for 18 hrs, in an automatically controlled electric oven, and quickly transferred into an oil bath of the same temperature 10 minutes before testing.

The tensile determinations were made on flat tensile specimens of 2 inch gage length which were cast in a cold iron mold from 400 C. The tests were carried out in an electrically heated and automatically controlled oil bath at 150 C. and 200 C. About 20 minutes were allowed for the specimens to reach temperature. The speed of the head of the tensile machine was such as to give an elongation in the specimen of 0.05 inch per inch of specimen per minute.

It will be seen from the above that the improved alloy shows definitely improved properties over the standard lead-base and tin-base babbitts at elevated temperatures both as to hardness and tensile strength.

The improved alloy shows also improved fatigue values, tests of this value being made on a standard R. R. Moore rotating beam type machine, the fatigue limit being taken as the stress which would not produce fracture in 20,000,000 cycles.

Under these conditions, lead-base babbitt showed a fatigue value range of 3,9004,000 p. s. i.; tin-base babbitt 3,400-3,500 p. s. i.; and the present alloy 4,400-4,500 p. s. i. The above values are at room temperatures.

Additionally, as bearings may be subjected to elevated temperatures for considerable periods of time, it is essential that their properties be stable at operating temperatures. The relative stability of lead-base babbitt, tin-base babbitt and the present improved alloy is indicated by their hardness upon prolonged maintenance at elevated temperatures. The following table gives some hardness measurements on these three alloys after heating for 18 hours, '7 and 46 days at 150 C. and tested at this temperature.

Brinell hardness number when heated to 150 C.1or

Composition erties of standard lead-base and tin-base bab- 18 hrs. 7days 46 days bitt.

, Lead-base babbitt 6.9-7.6 6.9-7.1 5. 6-6.0 Brinell hardness Tensile strength, Tin-base bflbbitt 9. 2-9.8 9.0-9.5 8. 8.5 N ,1, Present improved alloy 9. 8-10.4 9. 10.1 9.5 Composition 25 0. 150 0. 25 0. 150 0. 200 0. It will be seen from the above results that the present alloy is very stable, and doesnt lose its Lead-base babbitt. 6. -7-6 10,000 2,910 1,195 hardness to any substantial extent after pro- T' b' 2. -26 9.2-. 1 1,645 3 232 {$3,333, 3 8 9 8 0 3 338 longed sub ection to elevated temperatures at alloy 9,835 4,250 1.953 150 C., which would be the maximum temperature limit to which the bearings might be subjected when in service, whereas both lead-base and tin-base babbitt show substantial softening under the same conditions.

It may be said further that the present alloy may be regarded as being fundamentally a lead base-arsenic-antimony alloy, in which both the arsenic and antimony are present in substantial amounts, the sum of the arsenic and antimony content being not less than substantially 13%, and a stiffening element included in the leadarsenic-antimony base. Of these stiffening elements, tin has been found to be best both in respect to the matters of hardness, ductility and tensile strength under operating conditions, and as regards the casting properties of the alloy. Cadmium, if substituted for the tin, makes an alloy which perhaps might be thought to be somewhat comparable to the tin-containing a1- loy, but at best its peak of eflfectiveness is below that of tin and the cadmium-containing alloy markedly softens when aged for only a short time and its casting properties are inferior to those of the tin alloy. Many other elements stiffen the lead-arsenic-antimony base alloy, among which may be mentioned copper, tellurium, silver, nickel, and zinc. Small amounts of the tin may be replaced with any one of these elements but with some loss of desirable properties.

What is claimed is:

1. A lead-base alloy consisting of 6-16% antimony, 1.5-6% arsenic, the antimony and arsenic together totalling at least 13%, 02-25% tin, and lead.

2. A lead-base alloy consisting of 10-14% antimony, 25% arsenic, the composite amount of antimony and arsenic being at least 13%, 0.5- 0.9% tin, and lead.

3. A lead-base alloy consisting of approximately 12.5% antimony, approximately 3% arsenic, approximately 0.75% tin, and lead.

4. A bearing alloy of the following composition exclusive of minor impurities: 0.2% to 2.5% tin, 76.5% to 88.8% lead, 2% to 5% arsenic, and 9% to 16% antimony, the arsenic and antimony constituting at least 12.5% of the alloy.

ALBERT J. PHILLIPS. ALBERT A. SMITH, JR. PAUL A. BECK. 

